Nuclear Theory·nucl-th

Wednesday·April 27, 2016

10 papers—7 primary·3 cross-listed

08
Model independent analysis of nearly Lévy correlations
T. Novák🇭🇺 · T. Csörgő🇭🇺 · H. C. Eggers🇿🇦 · M. de Kock🇿🇦
A model-independent method for the analysis of the two-particle short-range correlations is presented, that can be utilized to describe e.g. Bose-Einstein (HBT), dynamical (ridge) or other correlation functions, that have a nearly Lévy or streched exponential shape. For the special case of Lévy exponent alpha = 1, the earlier Laguerre expansions are recovered, for the alpha = 2 special case, a new expansion method is obtained for nearly Gaussian correlation functions. Multi-dimensional Lévy expansions are also introduced and their potential application to analyze rigde correlation data is discussed.
↳ physics.data-anhep-exhep-phnucl-ex+1Acta Phys.Polon.Supp.(2016)·15 citations
09
Second-order hydrodynamics for fermionic cold atoms: Detailed analysis of transport coefficients and relaxation times
Yuta Kikuchi · Kyosuke Tsumura · Teiji Kunihiro
We give a detailed derivation of the second-order (local) hydrodynamics for Boltzmann equation with an external force by using the renormalization group method. In this method, we solve the Boltzmann equation faithfully to extract the hydrodynamics without recourse to any ansatz. Our method leads to microscopic expressions of not only all the transport coefficients that are of the same form as those in Chapman-Enskog method but also those of the viscous relaxation times $τ_{i}$ that admit physically natural interpretations. As an example, we apply our microscopic expressions to calculate the transport coefficients and the relaxation times of the cold fermionic atoms in a quantitative way, where the transition probability in the collision term is given explicitly in terms of the $s$ -wave scattering length $a_{s}$ . We thereby discuss the quantum statistical effects, temperature dependence, and scattering-length dependence of the first-order transport coefficients and the viscous relaxation times: It is shown that as the temperature is lowered, the transport coefficients and the relaxation times increase rapidly because Pauli principle acts effectively. On the other hand, as $a_{s}$ is increased, these quantities decrease and become vanishingly small at unitarity because of the strong coupling. The numerical calculation shows that the relation $τ_{π} = η / P$ , which is derived in the relaxation-time approximation and used in most of literature without almost any foundation, turns out to be satisfied quite well, while the similar relation for the relaxation time $τ_{J}$ of the heat conductivity is satisfied only approximately with a considerable error.
↳ cond-mat.quant-gasnucl-thphysics.flu-dyn0 citations
10
The Operator Product Expansion Beyond Leading Order for Two-Component Fermions
Samuel B. Emmons🇺🇸 · Daekyoung Kang🇺🇸 · Lucas Platter🇺🇸
We consider a homogeneous, balanced gas of strongly interacting fermions in two spin states interacting through a large scattering length. Finite range corrections are needed for a quantitative description of data which experiments and numerical simulations have provided. We use a perturbative field theoretical framework and a tool called the Operator Product Expansion (OPE), which together allow for the expression of finite range corrections to the universal relations and momentum distribution. Using the OPE, we derive the $1/ k^{6}$ part of the momentum tail, which is related to the sum of the derivative of the energy with respect to the finite range and the averaged kinetic energy of opposite spin pairs. By comparing the $1/ k^{4}$ term and the $1/ k^{6}$ correction in the momentum distribution to provided Quantum Monte Carlo (QMC) data, we show that including the $1/ k^{6}$ part offers marked improvements. Our field theoretical approach allows for a clear understanding of the role of the scattering length and finite effective range in the universal relations and the momentum distribution.
↳ cond-mat.quant-gashep-phnucl-thPRA(2016)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE

Model independent analysis of nearly Lévy correlations

Second-order hydrodynamics for fermionic cold atoms: Detailed analysis of transport coefficients and relaxation times

The Operator Product Expansion Beyond Leading Order for Two-Component Fermions

Affiliations